Single radio voice call continuity (SRVCC) permits a packet switched network operator to move voice services to a circuit switched network. SRVCC for voice calls was first defined in release 8 of the third generation partnership project (3GPP). SRVCC was extended in later releases, such as for voice calls in an alerting call state and for calls with active mid-call services, for example, hold, conferencing, etc. Further, 3GPP release 9 defined SRVCC for IMS emergency voice calls.
eCall is a European initiative intended to bring rapid assistance to motorists involved in a collision. eCall provides an emergency call service for vehicles and is defined in 3GPP and by the European Telecommunications Standards Institute (ETSI). eCall utilizes an audio codec to provide the emergency call service that is initiated from a vehicle and to provide certain information regarding the vehicle, such as the location of the vehicle, the vehicle identification number, etc. The eCall audio codec provides this information regarding the vehicle in-band in an emergency call, such as an IMS emergency voice call. This data is termed a minimum set of emergency related data (MSD). The MSD may be carried in various manners over IMS. For example, the initial MSD from the in-dash vehicle system (IVS) to the public safety answering point (PSAP) may be carried as the body of an INVITE message. In this example, the PSAP can subsequently require an update to the MSD during an ongoing eCall session with the updated MSD being carried in the body of an INFO transaction or a SUBSCRIBE/NOTIFY transaction.